(Bloomberg) -- President Joe Biden is expected to announce Thursday that federal workers will be required to prove they’ve been vaccinated against Covid-19 or submit to frequent coronavirus testing, according to a person familiar with the matter.

The decision comes after the Centers for Disease Control and Prevention tightened its mask guidance on Tuesday amid the spread of the highly contagious delta variant, which has caused cases to spike across the country. The plan for a vaccine mandate won’t be finalized until Thursday, the person said.

Biden said Tuesday he was considering a vaccine mandate for federal workers, and he’ll deliver a speech on the U.S. fight against the pandemic on Thursday. CNN and NBC News reported earlier that he would issue a vaccine mandate for federal workers.

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